package cn.com.code.leetcode;

/**
 * 2. 两数相加
 * https://leetcode.cn/problems/add-two-numbers/
 *
 * @author zhengpei
 * @date 2022/6/27
 */
public class LeetCode2 {

  public class ListNode {
    int val;
    ListNode next;

    ListNode() {
    }

    ListNode(int val) {
      this.val = val;
    }

    ListNode(int val, ListNode next) {
      this.val = val;
      this.next = next;
    }
  }

  public static void main(String[] args) {
  }

  public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    ListNode head = null, tail = null;
    int carry = 0;
    while (l1 != null || l2 != null) {
      int n1 = l1 != null ? l1.val : 0;
      int n2 = l2 != null ? l2.val : 0;
      int sum = n1 + n2 + carry;
      if (head == null) {
        head = tail = new ListNode(sum % 10);
      } else {
        tail.next = new ListNode(sum % 10);
        tail = tail.next;
      }
      carry = sum / 10;
      if (l1 != null) {
        l1 = l1.next;
      }
      if (l2 != null) {
        l2 = l2.next;
      }
    }
    if (carry > 0) {
      tail.next = new ListNode(carry);
    }
    return head;
  }
}